Modeling of S-RAM Energy Recover Compressor Integration in a Transcritical Carbon Dioxide Cycle for Application in Electronics Cooling in Varying Gravity

As electronics in military aircraft become increasingly complicated, additional cooling is necessary to enable efficient and high computing performance. Additionally, the varying forces that a military aircraft endure during maneuvering and inverted flight introduce unique design constraints to the electronics cooling systems. Because this cooling system will be in an aircraft, the capacity and unique design constraints must all be met with a design that is as lightweight as possible. This paper presents a study comparing the coefficient of performance (COP) of several cycle architectures with both R134a and carbon dioxide ( ). Cycles with single-stage and two-stage compression with intercooling are compared, and both are modeled with suction-to-liquid line heat exchangers. The cycles utilizing are transcritical in order to reach the required temperatures for heat rejection from the gas cooler. Additionally, cycles with expansion work recovery and an ejector are compared. The cooling requirements are up to 150 kW with a heat source temperature as low as and a heat sink temperature of up to . The purpose of this analysis is to understand which of the above cycles performs with the highest efficiency for the given electronics cooling application

Liquid flooded Ericsson cycle cooler

A novel approach to implementing a gas Ericsson cycle heat pump was developed. The concept, termed a liquid flooded Ericsson cooler (LFEC), uses liquid flooding of the compressor and expander to approach isothermal compression and expansion processes. Since the LFEC cycle has not been studied previously most of the work presented represents new contributions to the literature. The specific major contributions of the work can be summarized as follows. Analytical models of liquid flooded compression and expansion processes were developed, using ideal gas, constant specific heat, and incompressible liquid assumptions. Special considerations for fixed volume ratio positive displacement compressors are detailed. The unique behavior of a liquid flooded compressor was explored, including the discovery of an optimum liquid flooding rate that minimizes compression power. A computer model of the LFEC cycle was developed using ideal gas, incompressible liquid, and constant specific heat assumptions. The model was used for a thorough parameterc study. The purpose of the study was to explore the feasibility of the concept, identify the optimum operating parameters, and to provide the basis for the design of an experimental system. An experimental system was developed. It was believed to be the only system of its type in existence at the time of construction. Cooling capacities of up to 677 W were measured. Several factors related to the early state of development for the LFEC resulted in maximum second law efficiencies of only 3%. A second computer model of the LFEC was developed, which incorporated real fluid properties and additional parameters that were deemed necessary based on experimental observations. Two parametric studies were performed using this model. First, a parametric sensitivity study was performed to identify the minimum rotating machinery adiabatic efficiencies required to attain a COP of 1.25 for near ambient refrigeration applications. It was found that a well designed system with realistic losses could reach the target COP if the adiabatic efficiencies of the rotating machinery are equal or greater than 85%. The second parametric study, with the real fluid model, was used to identify the application (i.e. source temperature) for which the LFEC was most suited. It was found that when nonideal operation was assumed that the best second law efficiency for the LFEC occurs at source temperatures in the range of -90°C